Microstructure and properties of bainitic non-quenched and tempered steel with different section size

doi:10.13251/j.issn.0254-6051.2021.08.013

Abstract

Abstract: Microstructure and mechanical properties of the bainitic non-quenched and tempered steel bar with different diameters air-cooled at 920 ℃ and tempered at 300 ℃ were studied. The results show that the microstructure of the bainitic steel bar with different diameters after air cooling and tempering is the bainite ferrite and retained austenite, which belongs to non-carbide bainitic structure. The microstructure of the bars with diameter smaller than ϕ30 mm changes a little after heat treatment, but the core microstructure of the bars with diameter larger than ϕ50 mm becomes coarser and the amount of granular bainite increases. After heat treatment, with the increase of diameter, the strength and hardness of the bars tend to decrease. The impact absorbed energy of the bars with diameter larger than ϕ50 mm decreases with the increase of diameter. The tensile strength of the ϕ70 mm bar at R/2 is 1226 MPa, and the core impact absorbed energy is 61.3 J. Bainitic non-quenched and tempered steel with larger diameter has good combination of strength and toughness.

Key words: bainitic non-quenched and tempered steel, section size, microstructure, property

CLC Number:

TG142.1

Li Mengge, Cheng Juqiang, Yin Sibo. Microstructure and properties of bainitic non-quenched and tempered steel with different section size[J]. Heat Treatment of Metals, 2021, 46(8): 65-69.

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